Zeros of the pi /sup +/ pi /sup -/ to pi /sup +/ pi /sup -/ amplitude (from data on pp to pi /sup -/ pi /sup +/)

Recent data on the reaction pp to pi /sup -/ pi /sup +/ show four conspicuous dips in the angular distribution at fixed values of nu =t- u. The conjecture is made that the channel pi /sup -/ pi /sup +/ to pi /sup -/ pi /sup +/ has zeros at the same nu values. Using data of the CERN-Munich group, one can follow the zeros through the whole Mandelstam plane. The zeros pass through the intersections of s and t channel poles, as the Veneziano model predicts; however, away from these intersections, they propagate in a fashion systematically quite different from Veneziano's ansatz. (10 refs).